PEI / ULTEM

Expert

Polyetherimide

Ultra-polymer known for exceptional flame retardancy (UL94 V-0), high strength-to-weight ratio, and continuous use at ~170°C. ULTEM 9085 is certified for aerospace interior applications.

⚠ IMPORTANT: Dry Your Filament Before Every Print

All filaments — including PEI / ULTEM — absorb moisture from the air. Printing with wet filament causes stringing, bubbling, weak layer adhesion, and poor surface finish. This is the single most overlooked cause of bad prints.

Always dry your filament per the manufacturer's recommendations printed on the spool label before printing, especially if the spool has been open for more than a few days or stored in a humid environment. Read our complete filament drying guide →

About the Temperatures & Speeds Listed Below

The print temperatures and speeds shown on this page are general industry ranges — not a one-size-fits-all prescription. Every printer brand and model has different capabilities. A Bambu Lab X1C can print PLA at 500 mm/s; an Ender 3 with a Bowden extruder performs best at 40–80 mm/s.

Always follow your specific printer manufacturer's recommended settings and the temperature range printed on your filament spool label. Start at the lower end of the range and dial in from there.

Material Properties

Strength9/10

Flexibility2/10

Heat Resistance9/10

Printability1/10

Best For

Aircraft interiors (FAR 25.853 certified)
rail vehicle components
regulated flame-retardant applications

Avoid For

Open-air printing without an enclosure
Beginners / first prints

Pro Tips

01Requires nozzle capable of 390°C and chamber temp of 100°C+; standard desktop printers cannot meet these requirements
02Must be perfectly dry before printing; dry at 120°C for 12 hours
03Consistent, actively controlled chamber heating is essential; any temperature fluctuation causes failure

Print Speed by Printer Tier

Print speeds vary dramatically by printer. The speeds listed in product specs (like "500 mm/s") are maximum capabilities — not recommended everyday speeds. Use this table as a general guide and always follow your printer manufacturer's recommended settings.

High-End (Bambu X1C, P2S, H2D)

Print Speed: 150–300 mm/s

High-acceleration direct-drive systems. Follow manufacturer slicer presets.

Mid-Range (Bambu A1/A1 Mini, Prusa MK4, Creality K1)

Print Speed: 60–150 mm/s

Good performance at moderate speeds. Follow slicer presets for best results.

Entry-Level (Ender 3 series, Bowden extruders)

Print Speed: 30–60 mm/s

Start slow and tune up. Follow your printer manufacturer's recommended settings.

Quick Specs

Print Temp350–390°C

Bed Temp130–160°C

Cost / kg$150–$250

EnclosureRequired

DryingRequired

DifficultyExpert

Drying Note: Even filaments marked "Not Required" benefit from drying if the spool has been open or stored in a humid area. When in doubt, dry it.

Buy PEI / ULTEM Filament

Recommended brands: Hatchbox, eSUN, Polymaker, Bambu

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